METHODS AND REAGENTS FOR INHIBITING FURIN ENDOPROTEASE

Abstract: This invention relates to methods and reagents for inhibiting furin endoprotease activity and specifically for inhibiting furin endoprotease-mediated maturation of bioactive proteins in vivo and in vitro. The invention specifically provides proteins capable of inhibiting furin endoprotease activity. Particularly provided are alpha 1-antitrypsin variants that specifically inhibit furin endoprotease activity. Methods for using furin endoprotease inhibition to attenuate or prevent viral protein maturation, and thereby alleviate viral infections, are provided. Also provided are methods for using furin endoprotease inhibition to attenuate or prevent proteolytic processing of bacterial toxins, thereby alleviating bacterial infections. Methods are also provided to inhibit proteolytic processing of biologically active proteins and peptides. The invention also provides pharmaceutically acceptable compositions of therapeutically effective amounts of furin endoprotease inhibitors.

Description: METHODS AND REAGENTS FOR INHIBITING FURIN ENDOPROTEASE BACKGROUND OF THE INVENTION 5 This invention was made with government support under DK44629 and DK37274 from the National Institutes of Health. The government has certain rights in the invention. 10 1. Field of the Invention This invention relates to endoproteases, particularly a novel endoprotease termed furin endoprotease. The invention also relates to inhibitors of furin endoprotease activity. In particular, the invention relates to novel variants of α,- antitrypsin that specifically inhibit furin endoprotease activity. The invention also 15 provides methods for using such inhibitors to attenuate or prevent biological proteolytic maturation of bioactive proteins and peptides in vivo and in vitro, in particular viral proteins and bacterial toxins. Therapeutic methods and pharmaceutical compositions of such inhibitors are also provided directed towards the alleviation and treatment of disease having microbiological etiology. 20 2. Background of the Related Art Most biologically active peptides and proteins are synthesized initially as larger, inactive precursor proteins that are endoproteolytically cleaved during transit through the secretory pathway in the Golgi apparatus in cells expressing 25 such proteins (see Barr, 1991 , Cell 66: 1-3 for review). This system comprises an important common mechanism required for synthesis of biologically active proteins and peptides in yeast (Fuller et al., 1988, Ann. Rev. Physiol. 50: 345- 362), invertebrates (Scheller et al., 1983, Cell 32: 7-22) and mammalian cells (Sossin et a , 1989, Neuron 2: 1407-1417). Examples of proteins produced in " 30 vivo by exocytotic transport through the Golgi are precursors of peptide . hormones, neuropeptides, growth factors, coagulation factors, serum albumin, cell surface receptors, and adhesion molecules. Morrison et ah, 1985, J. Virol. 53: 851-857 disclose that F protein of Newcastle disease virus is processed through the exocytotic transport pathway in infected cells. Perez & Hunter, 1987, J. Virol. 6J.: 1609-1614 disclose that the Rous sarcoma virus (RSV) glycoprotein is processed through the exocytotic transport pathway in infected cells. Yamada et ah, 1988, Virology 16J>: 268-273 disclose that F protein of mumps virus is processed through the exocytotic transport pathway in infected cells. Randolph et ah, 1990, Virology 174: 450-458 disclose that the prM protein of flaviviruses is processed through the exocytotic transport pathway in infected cells. A common structural feature of molecules processed through the exocytotic transport pathway is the presence of basic residues or pairs of basic residues at the proteolytic processing site in the molecule. Examples include serum factors (Factor IX; Bentley et ah, 1986, Cell 4£: 343-348; proalbumin; Knowles et ah, 1980, Science 2Q9: 497-499; pro-von Willibrand factor; Bonthron et ah, 1986, Nature 224: 270-273), viral polyproteins (human immunodeficiency virus (HIV) gpl60; McCune et ah, 1988, Cell 52: 55-67; RSV envelope protein; Perez & Hunter, 1987, J. Virol. 61: 1609-1614; yellow fever virus protein; Rice et ah, 1985, Science 229: 726-733; measles virus protein; Richardson et ah, 1986, Virology 155: 508-523; mumps virus protein; Waxham et ah, 1987, Virology 159: 381-389; human cytomegalovirus protein; Spaete et ah, 1990, J. Virol. 64. 2922-2931; varicella zooster virus protein; Keller et ah, 1986, Virology 152: 181- 191), growth factors (pre-protransforming growth factor β; Gentry et ah, 1988, Molec. Cell. Biol. 8: 4162-4168; epidermal growth factor; Gray et ah, 1983, Nature 203: 722-725; pro-|S-nerve growth factor (NGF); Edwards et ah, 1988, Molec. Cell Biol. 8: 2456-2464), receptors (insulin receptor; Yoshimasa et a , 1988, Science 240: 784-787); and bacterial toxins [see Stephen & Pietrowski, 1986, Bacterial Toxins. 2d ed. (Amer. Soc. Microbiol. Washington, D.C.) for review; anthrax toxin; Singh et ah, 1989, J. Biol. Chem. 264: 11099-11102]. The proteolytic processing site has been identified in some of these molecules. Berger & Shooter, 1977, Proc. Natl. Acad. Sci. USA 74: 3647-3651 disclose the sequence -RSKR- at the proteolytic processing site of pro-0-NGF. Bentley et ah, 1986, ibid, disclose the sequence -RPKR- at the proteolytic processing site of the blood coagulation factor protein Factor IX. McCune et ah, 1988, ibid., disclose the sequence -REKR- at the proteolytic processing site of HIV gpl60. Clepak et ah, 1988, Biochem. Biophys. Res. Comm. 157: 747-754 disclose the sequence -RVRR- at the proteolytic processing site of diphtheria toxin. Vey et ah, 1992, Virology 188: 408-413 disclose the sequence - RX(R/K)R- at the proteolytic processing site of influenza hemagglutinin. Ogata et ah, 1990, J. Biol. Chem. 265: 20678-20685 disclose the sequence -RSKR- at the proteolytic processing site of Pseudomonas exotoxin A. Klimpel et ah, 1992, Proc. Natl. Acad. Sci. USA 89: 10277-10281 disclose the sequence -RX(R/K)R- at the proteolytic processing site of anthrax protective antigen. Recently, an endoprotease termed furin has been isolated that specifically recognizes the recognition sequence of proteins processed through the exocytotic secretory pathway (Wise et ah, 1990, Proc. Natl. Acad. Sci. USA 87: 9378- 9382; Bresnahan et ah, 1990, J. Cell Biol. Hi: 2851-2859). This endoprotease is a subtilisin-related, calcium-dependent serine protease (Bresnahan et ah, ibid.). A complementary DNA copy of the mRNA encoding this endoprotease has been isolated (Wise et ah, ibid.) and sequenced (van den Ouweland et ah, 1992, Nucleic Acids Res. 18: 664) and expressed in heterologous cells (Bresnahan et al. , ibid.). These studies have shown furin to be expressed as a doublet of 96 and 90 kilodaltons (kD) in size, ubiquitously expressed as a 4.5 kilobase (kb) mRNA, and localized by fluorescence immunohistochemistry to the Golgi apparatus of cells expressing this endoprotease (Bresnahan et ah, ibid.). Furin has been shown to be capable of proteolytically cleaving a number of exocytotically processed proteins. Bresnahan et ah, ibid., disclose furin-mediated cleavage of pro-0-NGF. Wise et al. , ibid. , disclose furin-mediated cleavage of pro-von Willibrand factor and complement factor C3. Hosaka et ah, 1991, J. Biol. Chem. 26£: 12127-12130 disclose furin- mediated cleavage of renin. Steineke-Grober et ah, 1992, EMBO J. 11: 2407-2414 disclose furin- mediated cleavage of influenza hemagglutinin. Klimpel et ah, 1992, Proc. Natl. Acad. Sci. USA 89: 10277-10281 disclose furin-mediated cleavage of anthrax protective antigen. Molloy et ah, 1992, J. Biol. Chem 267: 16396-16402 disclose furin- mediated cleavage of anthrax protective antigen. Klimpel et ah, 1992, Annual Meeting, Amer. Soc. Microbiol. Abst. B-32 disclose furin-mediated cleavage of diphtheria toxin. Furin can be inhibited by specific peptidyl chloroalkylketones (Garten et ah, 1989, Virology 172: 25-31; Molloy et ah, ibid.; Hallenberger et ah, 1992, Nature 26Q: 358-361), but these substances are toxic in vivo. Given the importance of this endoprotease in activation of bacterial toxins, viral structural proteins and bioactive molecules, there is a need for the development of safe and specific furin inhibitors. SUMMARY OF THE INVENTION This invention provides safe, specific and effective inhibitors of furin endoprotease that are novel variants of the naturally-occurring protease inhibitor, c. r antitryρsin (Heeb et ah, 1990, J. Biol. Chem 265: 2365-2369; Schapira et a , 1987, J. Clin. Invest. 80: 582-585) and peptides derived therefrom. Use of these novel variants of o.,-antitrypsin is advantageous because α]-antitrypsin and variants are secreted proteins that are processed by the exocytotic secretory pathway through the Golgi, so synthesis of these proteins in a cell would result in delivery of the inhibitor to the site of furin activity in vivo. In a first embodiment, the invention provides a furin endoprotease inhibitor comprising an α,-antitrypsin variant protein having an amino acid sequence comprising the amino acids of the native α r antitrypsin molecule (disclosed in Long et ah, 1984, Biochemistry 22: 4828-4837, incorporated by reference), except that the sequence at position 355-358 of the native protein (-Ala-Ile-Pro- Met-) is changed to the novel sequence -Arg-X-X-Arg-, wherein each X is any amino acid, at positions 355-358 of the native αrantitrypsin amino acid sequence. In a preferred embodiment, the αrantitrypsin variant is αj-antitrypsin Portland and the amino acid sequence at positions 355-358 of the αrantitrypsin amino acid Portland sequence is -Arg-Ue-Pro-Arg-. In a second embodiment, the invention provides a nucleic acid having a nucleotide sequence that encodes an α,-antitrypsin variant protein having an amino acid sequence comprising the amino acids of the native αrantitrypsin molecule, except that the sequence at position 355-358 of the native protein (-Ala-Ile-Pro- Met-) is changed to the novel sequence -Arg-X-X-Arg-, wherein each X is any amino acid, at positions 355-358 in the variant αrantitrypsin amino acid sequence. In a preferred embodiment, the αrantitrypsin variant is α,-antitrypsin Portland and the amino acid sequence is -Arg-Ile-Pro-Arg-. In a third embodiment, the invention provides a recombinant expression construct comprising a nucleic acid having a nucleotide sequence encoding an α r antitrypsin variant protein with an amino acid sequence comprising the amino acids of the native αrantitrypsin molecule, except that the sequence at position 355-358 of the native protein (-Ala-Ile-Pro-Met-) is changed to the novel sequence -Arg-X-X-Arg-, wherein each X is any amino acid, at positions 355-358 of the variant αrantitrypsin amino acid sequence. In a preferred embodiment, the α r antitrypsin variant is αrantitrypsin Portland and the amino acid sequence is -Arg- Ile-Pro-Arg-. The recombinant expression construct provided by the invention is capable of expressing αrantitrypsin variant proteins of the invention in a culture of transformed cells. In a preferred embodiment, the recombinant expression construct comprises a vaccinia virus-based construct. In a more preferred embodiment, the recombinant expression construct comprises a recombinant vaccinia virus vector covalently linked to the nucleic acid encoding the α r antitrypsin variant, preferably a r antitrypsin Portland. The invention also provides a cell culture transformed with the recombinant expression construct encoding an αrantitrypsin variant capable of expressing the α,-antitrypsin variant. In a preferred embodiment, the α r antitrypsin variant is α,-antitrypsin Portland. Preferred embodiments of such cell cultures are cultures of bacterial cells, yeast cells, insect cells or mammalian cells. In another embodiment, the invention provides a homogenous composition of matter comprising an αrantitrypsin variant produced by the cell culture according to the teachings of the invention. In a preferred embodiment, the α r antitrypsin variant is α,-antitτypsin Portland. The invention also provides a furin endoprotease inhibitor comprising α r antitrypsin variants capable of blocking endoproteolytic activation of bacterial toxins. In a preferred embodiment, the α,-antitrypsin variant is α,-antitrypsin Portland. Pharmaceutically acceptable compositions of the α,-antitrypsin variants of the invention are also provided comprising a therapeutically effective amount of αrantitrypsin variant and a pharmaceutically acceptable carrier or diluent. Also provided by the invention are peptides having an amino acid sequence of about 4 to about 100 amino acids in length, comprising the amino acid sequence -Arg-X-X-Arg-, wherein each X is any amino acid. In a preferred embodiment, the amino acid sequence is -Arg-Ile-Pro-Arg-. The invention provides a method of inhibiting bacterial infection of human cells comprising contacting such cells with an α,-antitrypsin variant of the invention. In a preferred embodiment, the α r antitrypsin variant is α,-antitrypsin Portland. In a preferred embodiment, the bacterial infection is caused by Corynebacterium diptheriae. In another preferred embodiment, the bacterial infection is caused by Bacillus anthracis. In yet another preferred embodiment, the bacterial infection is caused by Pseudomonas aeruginosa. The invention also provides a method of inhibiting bacterial infection in a human comprising administering a therapeutically effective amount of an α,- antitrypsin variant of the invention in a pharmaceutically acceptable carrier. In a preferred embodiment, the αrantitrypsin variant is α,-antitrypsin Portland. In a preferred embodiment, the bacterial infection is caused by Corynebacterium diptheriae. In another preferred embodiment, the bacterial infection is caused by Bacillus anthracis. In yet another preferred embodiment, the bacterial infection is caused by Pseudomonas aeruginosa. The invention provides a method of treating humans with a bacterial infection comprising administering a therapeutically effective amount of an α r antitrypsin variant of the invention in a pharmaceutically acceptable carrier. In a preferred embodiment, the αrantitrypsin variant is α r antitrypsin Portland. In a preferred embodiment, the bacterial infection is caused by Corynebacterium diptheriae. In another preferred embodiment, the bacterial infection is caused by Bacillus anthracis. In yet another preferred embodiment, the bacterial infection is caused by Pseudomonas aeruginosa. Another method provided by the invention for treating humans with a bacterial infection comprises administering a combination of a therapeutically effective amount of an α,-antitrypsin variant and a therapeutically effective amount of a second antibacterial compound in a pharmaceutically acceptable carrier. In a preferred embodiment, the αrantitrypsin variant is α,-antitrypsin Portland. In a preferred embodiment, the bacterial infection is caused by Corynebacterium diptheriae. In another preferred embodiment, the bacterial infection is caused by Bacillus anthracis. In yet another preferred embodiment, the bacterial infection is caused by Pseudomonas aeruginosa. Pharmaceutically acceptable compositions effective according to the methods of the invention, comprising a therapeutically effective amount of a furin endoprotease inhibitor capable of blocking endoproteolytic activation of bacterial toxins and a pharmaceutically acceptable carrier or diluent, are also provided. The invention provides a method of inhibiting viral infection of human cells comprising contacting such cells with an αrantitrypsin variant according to the invention. In a preferred embodiment, the invention provides a gene therapy delivery system for a nucleic acid encoding an α,-antitrypsin variant comprising the recombinant expression construct of the invention and genetic means for delivery and expression of the recombinant expression construct into the cells of an animal. A preferred α,-antitrypsin variant is α r antitrypsin Portland. Pharmaceutically acceptable compositions comprising a therapeutically effective amount of the gene therapy delivery system and a pharmaceutically acceptable carrier or diluent. In a preferred embodiment, the viral infection is caused by Human Immunodeficiency Virus 1 (HIV-1). In another preferred embodiment, the human cells are hematopoietic cells, most preferably T lymphocytes. Other preferred embodiments of viral infections include infection by influenza virus. The invention also provides a method for inhibiting viral infection in an animal, most preferably a human, comprising administering a therapeutically effective amount of the gene therapy delivery system of the invention in a pharmaceutically acceptable carrier. In a preferred embodiment, the virus is Human Immunodeficiency Virus 1 (HIV-1). In another preferred embodiment, the virus is cytomegalovirus. The invention provides a method of treating humans infected with a virus comprising administering a therapeutically effective amount of the gene therapy delivery system of the invention in a pharmaceutically acceptable carrier. In a preferred embodiment, the virus is Human Immunodeficiency Virus 1 (HIV-1). In another preferred embodiment, the virus is influenza virus. The invention provides a method of treating humans infected with a virus comprising administering a combination of a therapeutically effective amount of the gene therapy delivery system of the invention and a therapeutically effective amount of a second antiviral compound in a pharmaceutically acceptable carrier. In a preferred embodiment, the virus is Human Immunodeficiency Virus 1 (HIV- 1) and the second antiviral compound is azidothymidine. In another preferred embodiment, the virus is influenza virus. The invention also provides a method for treating virus-associated immunosuppression in a human comprising administering a therapeutically effective amount of the gene therapy delivery system of the invention in a pharmaceutically acceptable carrier. In a preferred embodiment, the virus is Human Immunodeficiency Virus 1 (HIV-1). Pharmaceutically acceptable compositions effective according to the methods of the invention, comprising a therapeutically effective amount of the gene therapy delivery system encoding α,-antitrypsin variants having antiviral properties and a pharmaceutically acceptable carrier or diluent, are also provided. In a preferred embodiment, the αrantitrypsin variant is a r antitrypsin Portland The invention also provides a method of inhibiting proteolytic processing of a biologically active protein or peptide in a cell comprising contacting such cells with the gene therapy delivery system of the invention. Preferred biologically active proteins are pro-jδ-nerve growth factor, blood coagulation factor protein Factor IX, pro-von Willibrand factor, complement factor C3 and renin. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 illustrates production of native αrantitrypsin (Lane 1), α,- antitrypsin Pittsburgh (Lane 2) and α r antitrypsin Portland (Lane 3) by BSC-40 cells infected with vaccinia virus recombinant constructs. Figure 2 shows inhibition of thrombin and furin by native αrantitrypsin (striped bars), a,-antitrypsin Pittsburgh (dotted bars) and α,-antitrypsin Portland (stipled bars) in vitro. Figure 3 is an SDS-PAGE analysis of inhibition showing proteolytic processing of pro-jS-NGF by αrantitrypsin and variants. Figure 4 depicts Western blot analysis showing inhibition of proteolytic processing of HIV gpl60 by α,-antitrypsin and variants. Figure 5 illustrates the experimental protocol for assaying the gp41- mediated fusogenic capacity of gpl60-producing IP/IR erythroleukemia cells to form syncytia with CD4 + human HeLa cells in the presence and absence of co- expressed α,-antitrypsin and variants. Figure 6 illustrates the results of the syncytium experiments described in Example 5. Figure 7 shows an autoradiograph of αrantitrypsin Portland-mediated inhibition of pro-/3-NGF proteolytic processing in VV:mNGF-infected BSC-40 cells (Panel A) and quantitation of these results as a percentage of the autoradiographic density of the processed band (/3-NGF) relative to the total autoradiographic density (the sum of the β-NGF band plus the pro-β-NGF band). Figure 8 depicts the structure of recombinant expression constructs pRep4ΔL/Rpα,-PIT and pRep4ΔL/Rpα,-PDX. Figure 9 illustrates HIV-infected cultures of HeLa CD4 + clone 1022 cells (Panel B) and two independent transfectants, PDX-4 (Panel C) and PDX-6 (Panel A) four days post-infection. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The production of proteins such as the α,-antitrypsin Portland from cloned genes by genetic engineering is well known. See, e.g. , U.S. Patent No. 4,761,371 to Bell et a at Col. 6 line 3 to Col. 9 line 65. (The disclosure of all U.S. patent references cited herein is to be incorporated herein by reference.) The discussion which follows is accordingly intended as an overview of this field, and is not intended to reflect the full state of the art. For the purposes of this discussion, the αrantitrypsin variant a r antitrypsin Portland will be used as an exemplar; it will be understood that the discussion applies to and the invention encompasses all the α,-antitrypsin variants of the invention. DNA which encodes α,-antitrypsin Portland may be obtained, in view of the instant disclosure, by chemical synthesis, or by in vitro mutagenesis as described in Example 2 herein of the native αrantitrypsin DNA sequence. Such native αrantitrypsin DNA can be obtained by screening reverse transcripts of mRNA from appropriate cells or cultured cell lines, by screening genomic libraries from appropriate cells, or by combinations of these procedures. Screening of mRNA or genomic DNA may be carried out with probes generated from the known α,-antitrypsin gene sequence. Probes may be labeled with a detectable group such as a fluorescent group, a radioactive atom or a chemiluminescent group in accordance with know procedures and used in conventional hybridization assays (see Sambrook et ah, 1990, Molecular Cloning: A Laboratory Manual. Cold Spring Harbor Laboratory Press, N.Y.). In the alternative, αrantitrypsin gene sequences may be obtained for in vitro mutagenesis by use of the polymerase chain reaction (PCR) procedure, with the PCR oligonucleotide primers being produced from the native α,-antitrypsin gene sequence. See U.S. Patent Nos. 4,683,195 to Mullis et al. and 4,683,202 to Mullis. α r antitrypsin variants such as αrantitrypsin Portland may be synthesized in host cells transformed with a recombinant expression construct comprising a DNA sequence encoding an αrantitrypsin variant. Such a recombinant expression construct can also be comprised of a vector that is a replicable DNA construct. Vectors are used herein either to amplify DNA encoding α,-antitrypsin Portland and/or to express DNA encoding α,-antitrypsin Portland. For the purposes of this invention, a recombinant expression construct is a replicable DNA construct in which a DNA sequence encoding an α,-antitrypsin variant is operably linked to suitable control sequences capable of effecting the expression of the αrantitrypsin variant in a suitable host. The need for such control sequences will vary depending upon the host selected and the transformation method chosen. Generally, control sequences include a transcriptional promoter, an optional operator sequence (in bacteria) or enhancer sequence (in eukaryotic cells) to control transcription, a sequence encoding suitable mRNA ribosomal binding sites, and sequences which control the termination of transcription and translation. Amplification vectors do not require expression control domains. All that is needed is the ability to replicate in a host, usually conferred by an origin of replication, and a selection gene to facilitate recognition of transformants. DNA regions are operably linked when they are functionally related to each other. For example: a promoter is operably linked to a coding sequence if it controls the transcription of the sequence; a ribosome binding site is operably linked to a coding sequence if it is positioned so as to permit translation. Generally, operably linked means contiguous and, in the case of leaders sequences, contiguous and in the same translation^ reading frame. Vectors useful for practicing the present invention include plasmids, viruses (including phage), retroviruses, and integratable DNA fragments (i.e. , fragments integratable into the host genome by homologous recombination). The vector may replicate and function independently of the host genome, or may, in some instances, integrate into the genome itself. Suitable vectors will contain replicon and control sequences which are derived from species compatible with the intended expression host. A preferred vector is the plasmid pZVneo, useful for producing recombinant expression constructs based on homologous recombination with vaccinia virus sequences. A preferred embodiment of the recombinant expression constructs of this invention comprise vaccinia virus sequences capable of infecting mammalian cells and expressing αrantitrypsin variant, as described below in Example 2. Transformed host cells are cells which have been transformed or transfected with a recombinant expression construct made using recombinant DNA techniques and comprising sequences encoding an αrantitrypsin variant. Transformed host cells may express α,-antitrypsin Portland, but host cells transformed for purposes of cloning or amplifying DNA need not express these sequences. Cultures of cells, including cells derived from multicellular organisms, are a desirable hosts for recombinant α,-antitrypsin Portland synthesis. In principal, any cell culture is useful that is capable of being transformed with an appropriate recombinant expression construct and expressing αrantitrypsin protein. The invention is preferably practiced with bacterial, yeast, insect or mammalian cells, however, mammalian cells are more preferred, as illustrated in the Examples. Propagation of bacteria and yeast is well known in the art, and propagation of- mammalian cells in cell culture has become a routine procedure. See Tissue Culture. Academic Press, Kruse & Patterson, editors (1973). Most preferred mammalian cells are BSC-40 African green monkey kidney cells, but other cells, such as human 293 cells, VERO and HeLa cells, Chinese hamster ovary (CHO) cell lines, and WI138, BHK, COS-7, CV, and MDCK cells, are also useful. The invention provides homogeneous compositions of α,-antitrypsin Portland produced by transformed cells as provided herein. Such homogeneous compositions are intended to be comprised of mammalian αrantitrypsin Portland protein that comprises at least 90% of the protein in such homogenous composition. The recombinant expression constructs of the present invention are useful in molecular biology to transform cells in vivo in an animal as a method for protecting the animal from viral or other infection in cells that express furin or a furin-like endoprotease activity that can be inhibited by αrantitrypsin Portland. The invention provides a gene therapy delivery system comprising the recombinant expression constructs of the invention in a configuration that enables safe and efficient introduction of these sequences into appropriate cells and expression of αrantitrypsin Portland. For such purposes, retroviral vectors as described in U.S. Patent No. 4,650,764 to Temin & Watanabe or U.S. Patent No. 4,861,719 to Miller may be employed, for example. The recombinant expression constructs of the invention may also be used in gene therapy carried out homologous recombination. See generally Thomas & Capecchi, 1987, Cell 51: 503-512; Bertling, 1987, Bioscience Reports 7: 107-112; Smithies et ah, 1985, Nature 212: 230-234. Additionally, alteration of endogenous α,-antitrypsin sequences to produce α,-antitrypsin Portland in cells carrying such altered α r antitrypsin sequences can also be achieved using homologous recombination or other techniques. Transgenic animals, the tissues of which express the α r antitrypsin Portland variant, are also envisioned as additional objects of this invention. The peptides of this invention may be generated and/or isolated by any means known in the art. It is within the skill of those of ordinary skill in the art to isolate or chemically synthesize a nucleic acid encoding each of the peptides of the invention. Such nucleic acids are advantageously utilized as components of recombinant expression constructs, wherein the nucleic acids are operably linked with transcriptional and/or translational control elements, whereby the recombinant expression constructs of the invention are capable of expressing the peptides of the invention in cultures of cells, preferably eukaryotic cells, most preferably mammalian cells, transformed with such recombinant expression constructs. The peptides of the invention may be advantageously synthesized by any of the chemical synthesis techniques known in the art, particularly solid-phase synthesis techniques, for example, using commercially-available automated peptide synthesizers. Such peptides may be provided as linear peptides encompassing the amino acid sequence -Arg-X-X-Arg-, where each X is any aminio acid. These peptides may also be provided in the form of combination peptides, wherein the peptides comprising the combination are linked in a linear fashion one to another, with or without separation by "spacer" amino acids allowing for selected conformational presentation. Also provided are branched-chain combinations, wherein the component peptides are covalently linked via functionalities in amino acid sidechains of the amino acids comprising the peptides. The invention also provides antibacterial and antiviral methods. The invention provides methods for blocking endoproteolytic activation of bacterial toxins. Bacterial targets of the antibacterial methods provided by this invention include but are not limited to any bacteria that produces an endoproteolytically- activated toxin, such as diptheria toxin produced by Corynebacterium diptheriae, exotoxin A of Pseudomonas aurigenosa, tetanus toxin, the enterotoxins of Escherichia coli and Vibrio cholerae, protective antigen of Bacillus anthracis and the neurotoxin and C2 toxin of Clostridium botulinum. Preferred toxins are those that are proteolytically processed at a consensus furin recognition site (-Arg-Xaa- Xaa-Arg i-). Preferred embodiments include Corynebacterium diptheriae, Pseudomonas aeruginosa and Bacillus anthracis. Viral targets of antiviral methods provided include but are not limited to picomaviruses (e.g. , poliovirus and rhinovirus); orthomyxoviruses (e.g. , influenza virus); paramyxoviruses (e.g. , measles virus and mumps virus); coronaviruses; rhabdoviruses (e.g. , rabies virus and vesicular stomatitis virus); togaviruses (e.g. , Semliki Forest virus and yellow fever virus); bunyaviruses (e.g. , California encephalitis virus) ; arenaviruses (e. g. , Lassa fever virus) ; rubella virus; reoviruses (e.g. , Colorado tick fever virus); hepatitis viruses; adenoviruses; herpesviruses (e.g. , herpes simplex virus); and oncogenic viruses, including papilloma viruses, RNA tumor viruses, or retroviruses, and lentiviruses (e.g. , human immune deficiency virus). The most preferred viruses are the human immunodeficiency viruses (HIV-1 and HIV-2). Cells intended to be protected by the methods provided by this invention include but are not limited to human, canine, bovine, murine, leporine, porcine, ovine, simian, feline, hircine, and equine cells. The preferred cells are human cells. More preferred cells are human T lymphocytes (T cells), and the most preferred human T cells are those human T cells expressing the cell surface antigen CD4. The methods of the present invention may be used to treat donated human blood or plasma to protect transfusion recipients from viral infection from contaminating virus. The methods of the present invention may be used to treat human semen to protect embryos derived from such semen, and mothers bearing such embryos or impregnated with such semen, from contaminating virus. In a preferred embodiment, the contaminating virus is HIV-1. The present invention provides methods for inhibiting viral infection in a human. The invention also provides for treating a human infected with a virus. Another embodiment of the present invention includes methods for treating immunosuppression in a human associated with viral infection. Yet another embodiment of the present invention provides a method of prophylaxis for treating a human exposed to infection with a virus, in particular those directly at risk of infection as a result of intimate contact with humans infected with a virus of tissues or bodily fluids contaminated by a virus. The preferred virus of these embodiments of the invention is HIV- 1. The invention provides pharmaceutically acceptable compositions effective for use with the methods provided by the invention comprising the peptides of the invention and a pharmaceutically acceptable carrier. The invention also provides methods for inhibiting proteolytic processing of a biologically active protein or peptide in a cell comprising contacting such cells with the gene therapy delivery system of the invention. The methods of the invention encompass inhibition of proteolytic processing of any biologically active molecule that is proteolytically processed by furin in vivo or in vitro, including but not limited to peptide hormones, neuropeptides, growth factors, coagulation factors, serum albumin, cell surface receptors, and adhesion molecules. Preferred biologically active proteins are pro-3-nerve growth factor, blood coagulation factor protein Factor IX, pro-von Willibrand factor, complement factor C3 and renin, for alleviation of pathological conditions and disease states in an animal, preferably a human, associated with over-expression, over-production or otherwise inappropriate synthesis of such biologically-active proteins. Preparation of pharmaceutically acceptable compositions provided by the present invention can be prepared using methods well known to those with skill in the art. Any of the common carriers such as sterile saline solution, plasma, etc., can be utilized for preparing the pharmaceutical compositions provided by the invention. Routes of administration include but are not limited to oral (including inhalation into the lungs), intravenous, parenteral, rectal, optical, aural and transdermal. The pharmaceutical compositions of the invention may be administered intravenously in any conventional medium for intravenous injection such as an aqueous saline medium, or in blood plasma medium. Such medium may also contain conventional pharmaceutical adjunct materials such as, for example, pharmaceutically acceptable salts to adjust the osmotic pressure, buffers, preservatives and the like. Among the preferred media are normal saline and plasma. The following Examples illustrate certain aspects of the above-described method and advantageous results (also disclosed in Anderson et ah, 1993, J. Biol. Chem. 268: 24887-24891). The following Examples are shown by way of illustration and not by way of limitation. EXAMPLE 1 Production of Furin Endoprotease in African Green Monkey Cells In Vitro Human furin was synthesized for inhibition experiments as described in Bresnahan et al. (1990, J. Cell Biol. UΛ: 2851-2859) and Molloy et a (1992, J. Biol. Chem. 267: 16396-14402; both hereby incorporated by reference). Briefly, a furin cDNA (van den Ouweland et ah, 1992, Nucleic Acids Res. 18: 664) encoding a truncated but functional furin protein was inserted into the multiple cloning site of a vaccinia virus vector (see Hruby et ah, 1986, Meth. Enzymol. 124: 295-309) and used to infect BSC-40 African green monkey kidney cells (ATCC Accession No. CCL 26, American Type Culture Collection, Rockville, MD). The cells were incubated in serum-free defined media for 24 hours and then harvested at 4°C and disrupted by 20-30 strokes in a Dounce homogenizer (Kontes Glass Co., Vineland, OH). The lysate was cleared by low- speed centrifugation (lOOOg, 5 min) and the supernatant then subjected to ultracentrifugation at 100,000g for 1 hr. The pellet was resuspended in 200μL of a buffer comprising lOmM HEPES [N-(2-hydroxyethyl)piperazine-N'-(2- ethanesulfonic acid), Sigma Chemical Co., St. Louis, MO], pH 7.5 and stored at 4°C until use. Alternatively, a soluble, truncated derivative of furin lacking the carboxyl- terminal 81 amino acids was used (see Molloy et ah, ibid., incorporated by reference, for a more detailed description of this molecule). Briefly, BSC-40 cells were infected with a vaccinia virus vector containing the truncated furin cDΝA, grown for 16-18 h in serum-free defined media and then harvested. The cells were disrupted and subjected sequentially to centrifugation at lOOOg and 10,000g at 4°C. The supernatant was passed through a 0.2μm filter and then diluted approximately 1: 1 with a buffer consisting of 20mM BisTris (pH 7.0) and ImM 2-mercaptoethanol. This mixture was then applied to a Mono Q HR 5/5 fast protein liquid chromatography anion exchange column (Pharmacia LKB Biotechnology Inc.) and the truncated furin derivative eluted with a gradient of 0-750mM sodium chloride and stored at 4°C until use. EXAMPLE 2 In Vitro Mutagenesis and Production of Native and Variant Species of ofi-Antitrvpsin A novel α,-antitrypsin variant, termed α,-antitrypsin Portland, was produced by in vitro mutagenesis of a cloned cDNA encoding the naturally- occurring variant α,-antitrypsin Pittsburgh (Lewis et ah, 1978, Blood 51: 129- 137; Owen et ah, 1983, N. Engl. J. Med. 209: 694-698). A full length cDNA encoding αrantitrypsin Pittsburgh (which is identical to the sequence disclosed in Long et al. , supra, except for a Met 35g → Arg 358 mutation) was subcloned into M13mpl9 phage using standard techniques (see Sambrook et a , ibid. , Chapter 15). The following mutagenesis primer was then annealed to the sequence of single-stranded phage DNA corresponding to codons 352-358 of the α r antitrypsin Pittsburgh sequence: 5 '-TTTTTAG AG£G£ATACCCAG-3 ' (SEQ ID No: l) The underlined sequence encodes the mutagenized codon. After annealing, the mutagenesis primer was extended using the Klenow fragment of E. coli DNA polymerase in the presence of the four deoxynucleotide triphosphates. Clones having the mutagenized sequence were then grown and selected in E. coli, and DNA sequencing of the appropriate portion of the sequence of selected mutagenized clones was performed to confirm successful mutagenesis. The mutagenized α,-antitrypsin cDNA sequences were then subcloned into the vaccinia virus recombination vector pZVneo and used to produce vaccinia virus recombinants as described in Example 1 (and described in more detail in Hayflick et ah, 1992, J. Neurosci. 12: 705-717, hereby incorporated by reference). As a result of mutagenesis, the sequence of α,-antitrypsin Pittsburgh (Ala 355 -Ile-Pro-Arg 35g ) was changed to the novel sequence of α,-antitrypsin Portland (Arg 355 -Ile-Pro-Arg 358 ). Vaccinia virus constructs containing native α r antitrypsin (VV:αrNAT; Ala 355 -Ile-Pro-Met 3 j 8 ), αrantitrypsin Pittsburgh (VV:α PIT) and α,-antitrypsin Portland (VV:α,-PDX) were each used to infect BSC-40 cells. Such infected cells secrete each of the a,-antitrypsins into the culture media, and native αrantitrypsin and variants were isolated from culture media from appropriately-infected BSC-40 cells by passage of such media over a Mono Q HR 5/5 high pressure liquid chromatography anion exchange column (Pharmacia LKB Biotechnology Ltd., Stockholm, Sweden) and eluted using a linear gradient (0.05 -> 0.5M) of sodium chloride in 50mM Tris-HCl (pH 8.0), as described further in Molloy et a Production of native αrantitrypsin (Lane 1) and variants Pittsburgh (Lane 2) and Portland (Lane 3) was confirmed by Western blot hybridization (see Sambrook et ah, ibid., Chapter 18) as shown in Figure 1. EXAMPLE 3 In Vitro Characterization of Furin Endoprotease Inhibition by o_ r Antitrvpsin Portland α,-antitrypsin and variants Pittsburgh and Portland were assayed for the ability to inhibit furin endoprotease in vitro essentially as described in Molloy et al. (ibid.). Briefly, 25μL of the resuspended furin preparation described in Example 1 was incubated with each of the α r antitrypsins (at a final concentration of 10 / ig/mL) for 20 min at 37°C in a buffer comprising lOOmM HEPES (pH 7.5), ImM CaCl 2 , ImM 2-mercaptoethanol and 0.5% Triton-X 100. Substrate [(N-butoxycarbonyl)-Arg-Val-Arg-Arg-(4-methylcoumaryl-7-amide); Peninsula Laboratories, Belmont, CA] was then added to a final concentration of 50 μM and incubated for 30 min at 37 °C. The amount of liberated aminomethylcoumarin was then determined by fluorimetry (excitation wavelength = 380nm; emission wavelength = 460nm) using a spectrofluorimeter (Perkin Elmer, Waterbury, CT, Model LS3). The results of this experiment are shown in Figure 2. For comparison, each of the α,-antitrypsins were also incubated with thrombin and assayed for thrombin peptidase activity colorometrically using benzøy/-Phe-Val- Arg-(pαrø-nitroanilide) as substrate. These results are also shown in Figure 2. Native α,-antitrypsin was unable to inhibit either furin or thrombin endoprotease activity (striped bars), αrantitrypsin Pittsburgh specifically inhibited thrombin but not furin (dotted bars). The novel variant αrantitrypsin Portland (stipled bars) had no effect on thrombin endoprotease activity, but specifically and essentially quantitatively inhibited furin endoprotease activity. Table I provides the results of a comparison between the levels of inhibition of elastase [assayed colorometrically with (N-butoxycarbonyl)-Ala-Ala-Pro-Ala-(porα-nitroanilide) as substrate]. Elastase activity was specifically inhibited by native α,-antitrypsin (α r ΝAT), thrombin was specifically inhibited by αrantitrypsin Pittsburgh (α,-PIT), and furin was specifically inhibited by α,-antitrypsin Portland (α,-PDX). α,-PDX was found to be greater than 3000-fold more effective than α r PIT in inhibiting furin, having a K. Λ of 0.03 g/mL, equivalent to 0.4nM). α r PDX is also greatly attenutated in thrombin inhibitory activity ( > 300-fold) compared with α r PIT. TABLE I a = relative concentration of each serpin inhibitor 10 b = percent endoprotease activity in presence of each serpin These results demonstrated that the novel α,-antitrypsin structural variant (α r PDX) disclosed herein has novel functional properties that make it useful as a specific furin endoprotease inhibitor. EXAMPLE 4 In Vivo Characterization of Furin Endoprotease Inhibition bv o-rAntitrvpsin Portland αj-antitrypsin Portland was assayed for the ability to inhibit furin endoprotease in vivo. BSC-40 cells were co-infected with a vaccinia virus vector encoding the αrantitrypsin Portland as described in Example 2 and a vaccinia virus vector encoding pro- 3-nerve growth factor (0-NGF), a neuropeptide growth factor known to be processed by furin at the consensus furin site -Arg-Ser-Lys- Arg *- (Bresnahan et ah, ibid.) and secreted into the cell growth media. Co- infected cells were incubated in the presence of [ 35 S]-methionine for 4 h after infection and the cell media harvested. Media samples were then immunoprecipitated with NGF-specific antibodies and assayed by sodium dodecyl sulfate/ polyacrylamide gel electrophoresis (SDS-PAGE) and visualized by fluorography using standard techniques (as described in Sambrook et ah, ibid.). The results of these experiments are shown in Figure 3. Cells infected with wild-type vaccinia virus secreted no detectable iS-NGF into the culture media (Lane A), whereas cells infected with the vaccinia virus vector encoding 3-NGF secreted both processed (13 kilodaltons, kD) and unprocessed (* 35 kD) forms of jδ-NGF; co-infection of such cells with wild-type vaccinia virus had no effect on this pattern of β-NGF production (Lane C). Similarly, BSC-40 cells co- infected with the j8-NGF construct and with vaccinia virus constructs encoding native αrantitrypsin (Lane D) and αrantitrypsin Pittsburgh (Lane E) also produced both the processed and unprocessed forms of 0-NGF. In contrast, cells co-infected with the /3-NGF construct and with vaccinia virus constructs encoding αrantitrypsin Portland (Lane F) produced only the unprocessed form of β-NGF, demonstrating that α,-antitrypsin Portland is capable of inhibiting furin-mediated endoprotease processing of bioactive pro-peptides in vivo. EXAMPLE 5 Inhibition of Furin-Mediated Processing of Human Immunodeficiency Virus gpl60 bv o_,-Antitrvpsin Portland The experiments described in Example 4 were repeated using a vaccinia virus construct encoding the Human Immunodeficiency virus (HIV-1) glycoprotein gpl60. This precursor protein is known to be proteolytically processed into two membrane-associated proteins: gpl20 (which binds the HIV receptor CD4 on the cell surface of target host cells) and gp41 (which provides a fusogenic activity that mediates viral entry into the cell) in vivo. Proteolytic processing at the furin consensus site -Arg-Glu-Lys-Arg J - is a necessary step in maturation and release of HIV viral particles. Cell membranes from cells infected with vaccinia virus constructs were isolated as described in Example 1. Proteins from such membrane preparations were resolved by SDS-PAGE and specifically identified by Western blot analysis (see Sambrook et ah, ibid., Chapter 18) using antibodies against HIV proteins (see Anderson et ah, supra). The results of this experiment are shown in Figure 4. Cells infected with wild-type vaccinia virus produced no detectable HIV-related peptides (Lane A). In cells infected with the vaccinia virus vector encoding gpl60, both the unprocessed protein and processing products, gpl20 and gp41 were produced. BSC-40 cells co-infected with the gpl60 construct and with vaccinia virus constructs encoding native αrantitrypsin (Lane C) and α,-antitrypsin Pittsburgh (Lane D) also produced both unprocessed gpl60 and processed gpl20 and gp41. Cells co-infected with the gpl60 construct and with vaccinia virus constructs encoding α,-antitrypsin Portland (Lane E), on the other hand, produced only unprocessed gpl60. These results demonstrated that α,-antitrypsin Portland is capable of inhibiting furin-mediated endoprotease processing of bioactive viral proteins in vivo, and immediately suggested a method for treating viral infection by inhibiting viral protein processing. In another series of experiments, αrantitrypsin Portland-mediated inhibition of proteolytic processing of gpl60 was assayed to determine the functional consequences of such inhibition. As described above, processing of gpl60 results in the production of gp41, a protein that provides a fusogenic activity important for viral entry into target cells. Expression of gpl20 and gp41 on the surface of IP/IR erythroleukemia cells (see Spiro et ah, 1988, J. Virol. 6.3: 4434-4437) promotes cell fusion and syncytium formation with cells expressing the gpl20 target, CD4, at the cell surface. In these experiments, IP/IR cells were co-infected with vaccinia virus expression constructs encoding gpl60 and each of the aj-antitrypsins to determine the effect of inhibition of gpl60 processing on the fusogenic capacity of the cells. This experimental protocol is shown in Figure 5. Briefly, IP/IR cells were co-infected with the vaccinia virus gpl60 construct, either alone or co-infected with each of the αrantitrypsin constructs described in Example 2. The cells were incubated for 8-16 hours, collected and then overlaid onto a monolayer of CD4 + human HeLa cells [a modification of parental HeLa cells (ATCC No. CCL 2) that express the CD4 cell surface protein, as described in Kabat et ah, 1994, J. Virol. : - ). These cells were incubated for an additional 8-12 hours, and syncytium formation detected by staining with crystal violet and observed by phase-contract microscopy. The results of these experiments are shown in Figure 6. Panel A shows the results of HeLa/CD4 + cell overlay with IP/IR cells infected with vaccinia virus recombinants encoding HIV gpl60, and Panel B shows results of HeLa CD4 + cell overlay experiments using IP/IR cells infected with HIV gpl60 vaccinia recombinants co-infected with wild type vaccinia virus. Syncytia formation (and hence proper proteolytic processing of gpl60 to gpl20 and gp41) in the cells of each of these infected co-cultures was evidenced by the large number of multinucleated cells in each of the cultures. Panel C shows the results of HeLa/CD4 + cell overlay experiments using IP/IR cells infected with wild-type vaccinia virus; essentially no multinucleated cells were seen in such cultures. Panels D and E show the results of HeLa CD4 + cell overlay experiments using IP/IR cells co-infected with vaccinia virus recombinants encoding gpl60 and native (Panel C) and the Pittsburgh variant (Panel D) of α,-antitrypsin. Co- expression of native or variant Pittsburgh αrantitrypsin had no effect on syncytia formation caused by gp41. Panel F shows the effect on HIV gp41 -mediated syncytia formation of HeLa CD4 + cell overlay experiments using IP/IR cells co- infected with vaccinia virus recombinants encoding gpl60 and α antitrypsin Portland in HeLa/CD4 + cells. Syncytia formation is completely abolished in these cultures, and the cells of such cultures looked identical to cells in overlay experiments using IP/IR cells infected with wild-type vaccinia virus as seen in Panel C. These results demonstrate that inhibition of gpl60 processing by α r antitrypsin Portland eliminates the fusogenic activity of viral gp41 and suggests that such inhibition may provide a method for treating HIV infection in vivo and in vitro. EXAMPLE 6 Inhibition of Furin-Mediated Processing of jS-Nerve Growth Factor by Direct Application of αrAntitrvpsin Portland The ability of α,-antitrypsin Portland to inhibit proteolytic processing by addition of the inhibitor to the cellular growth media was demonstrated in the following assay. BSC-40 cells were grown to confluence in 35mm tissue culture plates (Falcon Microbiological Supply Co., Lincoln Park, NJ) and then infected with recombinant vaccinia virus encoding a functional pro-jS-NGF protein (VV:mNGF) as described in Example 4. Four hours prior to infection, the cellular growth media was removed and replaced with serum-free defined media (MCDB 202 media, made as described in McKeeton et ah, 1977, Dev. Biol. Std. 27: 97-108) supplemented with either 0, 0.5 or 50 μg/mL α r antitrypsin Portland (α j -PDX), prepared as described in Example 2. After this 4 h incubation, the cells were infected with VV:mNGF at a multiplicity of infection of 5 pfu/cell. In one culture, the pre-incubated cells were transfected with VV:mNGF at a m.o.i. of 2 and co-infected with VV:α,-PDX (see Example 2) at a m.o.i. of 5. After virus inoculation, α,-PDX was added to the culture media of each infected plate at the same concentration as in the pre-incubation period. Eighteen hours post-infection the media was removed from each plate and the cells metabolically labeled by incubation for 5 h in media containing [ 35 S]- methionine and [ 3S S]-cysteine (500μCi) and α,-PDX at the appropriate concentration for each plate. After labeling, the culture media from each plate was harvested and NGF peptides immunoprecipitated, resolved by SDS-PAGEand visualized by fluorography as described in Example 4. The results of this experiment are shown in Figure 7. Panel A is an autoradiograph of SDS-P AGE analysis of immunoprecipitated NGF peptides from each of the infected cultures, in which lane 1 contains the results from the culture incubated with αrPDX at 0 μg/mL; lane 2 contains the results from the culture incubated with αr X at 0.5 μg/mL; lane 3 contains the results from the culture incubated with αrPDX at 50 μg/mL; and lane 4 contains the results from the culture co-infected with VV:α,-PDX. As this autoradiographic evidence shows, incubation of cell cultures with α r PDX protein resulted in marked attenuation of furin-directed proteolytic processing of pro-3-NGF in a dose-dependent manner. The autoradiographic data was quantitated by densitometry as shown in Panel B; the percent relative amount of inhibition of proteolytic processing is represented as a percentage of the density of the processed ((S-NGF) band relative to the density of the sum of the processed plus the unprocessed (pro-/3-NGF) band. The Figure shows that α,-PDX at 50 μg/mL reduces the amount of proteolytic processing about five-fold [47% (0 μg/mL) versus 10% (50 μg/mL)]. Essentially no processing is seen in the co-infected cell line, consistent with the results described in Example 4 above. This dose-dependent attenuation of furin-directed proteolytic processing following administration of α,-PDX protein directly to cells in culture demonstrates the feasibility of a protein-based therapeutic approach directed at inhibiting furin-directed proteolytic maturation of a variety of biologically- important protein molecules, which is additionally advantageous due to the lack of thrombin inhibition exhibited by α,-PDX protein as disclosed herein. EXAMPLE 7 Construction of an HIV-LTR-based Recombinant Expression Vector Encoding ffrApUtrypsto Portland In order to stably transfect cells with a recombinant expression construct capable of expressing α PDX protein in vivo, the following expression vector was made, wherein expression of α,-PDX was mediated by the long terminal repeat (LTR) sequences of HIV-2. The completed plasmid is shown in Figure 8. A 470bp fragment was excised from the recombinant plasmid pGEM/RRE by SmallHindllϊ digestion and then blunt-end cloned into the BaniΑl site of the plasmid pRep4 (Invitrogen, San Diego, CA). Restriction enzyme-generated overhangs were blunt-ended using Klenow polymerase (Pharmacia, Upsala, Sweden) using conventional techniques (see Sambrook et ah). The 470bp fragment contains the rev responsive element of HIV-HXB2, comprising nucleotides 7621-8140 (Malim et ah, 1989, Nature 22& 254-257). The Rous Sarcoma Virus 3' LTR was excised from the resulting plasmid by a Sail (partial blunt)/Hi/»dIII digest, and replaced by ligation with an £cøRI(blunt)/HrødIII digestion fragment from pBennCAT (NIΗ AIDS Research Program, Bethesda, MD) containing the ΗIV LTR (nucleotides -450 to +80). The resulting expression plasmid was termed pRep4/RRE. Plasmids capable of expressing α,-PIT or α,-PDX cDNAs were constructed by inserting each of the cDNA molecules into pRep4/RRE between the ΗIV LTR and the RRE sequence in the proper orientation. This was done by excising α,-PIT cDNA sequences from pAIAT PIT (Long et ah, supra) using EcόBl (blunt) and Xhol digestion, or by excising α,-PDX cDNA sequences from pAIAT PDX using Smal and Xhol digestion, and cloning each cDNA into HmdIII (blunt)/XføI-digested pRep4/RRE. In a final step, the Epstein Barr virus origin of replication (ORIP) and nuclear antigen (EBNA-1) sequences were excised from the final versions of each of the α,-antitrypsin variant expression constructs as follows. pRep4/RRE was digested with Spel and Clά , blunt-ended as described above, and religated to itself (see Figure 8). A XballSacll fragment from the pRep4/RRE plasmid so modified was then swapped for the corresponding fragment in each of the a,-antitrypsin variant plasmids described above. This resulted in plasmids having the structure illustrated in Figure 8 and encoding each of the αrantitrypsin variants αrPIT (plasmid pRep4ΔL/Rpα,-PrT) and α r PDX (plasmid pRep4ΔL/Rpα,-PDX). EXAMPLE 8 Establishment of Human CD4 + Cell Lines Expressing The pRep4ΔL/Rpα,-PDX plasmid contains a functional hygromycin resistance gene (see Figure 8) capable of conferring hygromycin resistance to eukaryotic cells (see Product Catalog, Invitrogen). Ten micrograms of this plasmid DNA were introduced into HeLa/CD4 + clone 1022 cells (described in Example 5 above) using a modified calcium phosphate precipitation technique (Chen & Okayama, 1988, Molec. Cell. Biol. £: 123-130, as further described in Sambrook et ah, ibid.). Two days after transfection the cells were placed on selective media RPMI60/10% fetal calf serum supplemented with 100 μg/mL hygromycin (Sigma Chemical Co.) and maintained in this media throughout the experiment. Cell clones resistant to the drug appeared after about two weeks in selective media, and individual clones were isolated and expanded for subsequent experiments using conventional techniques [see Tissue Culture. Academic Press, Kruse & Patterson, editors (1973)]. Two such clones (termed PDX-4 and PDX-6) were used in the following experiments. Cell lines PDX-4, PDX-6 and parental HeLa CD4 + clone 1022 were seeded in 6-well plates (Falcon) at a density of 2 x 10 5 cells/plate. Cells cultures were then infected in duplicate with 2mL of media containing HIV strain LAV (NIH AIDS Research Program) having a reverse transcriptase activity of about 70,000 cpm/mL. Cell cultures were examined four days post-infection for cytopathic effects and syncytia formation. Such cultures are shown in Figure 9. The parental HeLa clone 1022 cells (Panel B) exhibited numerous syncytia and cytopathic loss of the cell monolayer. Both PDX-4 (Panel C) and PDX-6 (Panel A) cell cultures, on the other hand, showed few syncytia. Productive infection was verified by the detection of more than 250 pg/mL of the HIV core antigen, p24, in supematants from each of the infected cultures. The levels of infectious virus, in contrast, were much lower in the PDX-4 and PDX-6 cultures than in the parental HeLa clone 1022 culture. Cell lysates were prepared from each of the cell cultures on the fourth day post-infection and examined for the presence of gpl60/gpl20 by Western blot analysis as described in Example 5. Both gpl60 and gpl20 were detected in HIV-infected HeLa clone 1022 cultures, while no gpl20 and only a faint band corresponding to gpl60 was found in HIV-infected PDX-4 and PDX-6 cultures. These results demonstrated that expression of α PDX in HeLa clone 1022 cells conferred resistance in these cells to HIV infection. Moreover, the presence of p24 antigen in the cell supematants of such cultures in the absence of large amounts of infectious vims indicates that expression of αrantitrypsin Portland in these cells inhibits the formation of infectious enveloped vims particles. These results have important implications for preventing HIV infection of vulnerable cells both in vivo and in vitro. It should be understood that the foregoing disclosure emphasizes certain specific embodiments of the invention and that all modifications or alternatives equivalent thereto are within the spirit and scope of the invention as set forth in the appended claims.

Claims: WHAT WE CLAIM IS: 1. A furin endoprotease inhibitor comprising an αrantitrypsin variant protein or peptide fragment thereof having an amino acid sequence comprising the amino acids -Arg-X-X-Arg-, wherein each X is any amino acid, corresponding to positions 355-358 of the native αrantitrypsin amino acid sequence. 2. The furin endoprotease inhibitor of Claim 1 that is αrantitrypsin Portland wherein the amino acid sequence of αj-antitrypsin Portland at positions 355-358 of the native α r antitrypsin amino acid sequence is -Arg-Ile-Pro-Arg-. 3. A nucleic acid having a nucleotide sequence that encodes an α,- antitrypsin variant protein or peptide fragment thereof, wherein the amino acid sequence encoded by the nucleic acid has the sequence -Arg-X-X-Arg-, where each X is any amino acid, corresponding to positions 355-358 of the native α r antitrypsin amino acid sequence. 4. The nucleic acid of Claim 3 that is αrantitrypsin Portland wherein the amino acid sequence of a,-antitrypsin Portland encoded by the nucleic acid has the sequence -Arg-Ile-Pro-Arg- at positions 355-358 of the native α,- antitrypsin amino acid sequence. 5. A recombinant expression construct comprising a nucleic acid having a nucleotide sequence encoding an α,-antitrypsin variant protein or peptide fragment thereof, wherein the amino acid sequence encoded by the nucleotide sequence comprises the amino acids -Arg-X-X-Arg-, wherein each X is any amino acid, corresponding to positions 355-358 of the native αrantitrypsin amino acid sequence. 6. The recombinant expression construct of Claim 5 that is α r antitrypsin Portland wherein the amino acid sequence of αrantitrypsin Portland encoded by the nucleotide sequence comprises the amino acids -Arg-Ile-Pro-Arg- at positions 355-358 of the native αrantitrypsin amino acid sequence. 7. A recombinant expression construct comprising the nucleic acid of Claim 3, wherein the construct is capable of expressing αrantitrypsin Portland in a culture of transformed cells. 8. A cell culture transformed with the recombinant expression constmct of Claim 5, wherein the transformed cell culture is capable of expressing αrantitrypsin Portland. 9. The cell culture of Claim 8 comprising bacterial cells, yeast cells, insect cells or mammalian cells. 10. A homogenous composition of matter comprising α,-antitrypsin Portland produced by the cell culture of Claim 8. 11. A furin endoprotease inhibitor according to Claim 1 capable of blocking endoproteolytic activation of a bacterial toxin. 12. The furin endoprotease inhibitor of Claim 11 wherein the bacterial toxin is diptheria toxin of Corynebacterium diptheriae. 13. The furin endoprotease inhibitor of Claim 11 wherein the bacterial toxin is anthrax toxin of Bacillus anthracis. 14. A pharmaceutically acceptable composition comprising a therapeutically effective amount of the furin endoprotease inhibitor of Claim 11 and a pharmaceutically acceptable carrier or diluent. 15. A gene therapy delivery system for a nucleic acid encoding an α r antitrypsin variant comprising the recombinant expression constmct of Claim 5 and genetic means for delivery and expression of the recombinant expression constmct into the cells of an animal. 16. The gene therapy delivery system of Claim 15 wherein the antitrypsin variant is αrantitrypsin Portland. 17. A method of inhibiting bacterial infection of cells comprising contacting the cells with the furin endoprotease inhibitor of Claim 11. 18. A method of inhibiting viral infection of cells comprising contacting such cells with the gene therapy delivery system of Claim 15. 19. A method of inhibiting proteolytic processing of a biologically active protein or peptide in a cell comprising contacting such cells with the gene therapy delivery system of Claim 15. 20. The method of Claim 19 wherein the biologically active protein is pro-0-nerve growth factor, blood coagulation factor protein Factor IX, pro- von Willibrand factor, complement factor C3 or renin. 21. A peptide having an amino acid sequence of 4 to 100 amino acids comprising the amino acid sequence -Arg-X-X-Arg-, wherein each X is any amino acid.

Inventors: ANDERSON ERIC D, HAYFLICK JOEL S, NELSON JAY, STENGLEN STEPHAN G, THOMAS GARY, THOMAS LAUREL, ANDERSON, ERIC, D., HAYFLICK, JOEL, S., NELSON, JAY, STENGLEN, STEPHAN, G., THOMAS, GARY, THOMAS, LAUREL
Applicants: ANDERSON ERIC D, HAYFLICK JOEL S, NELSON JAY, OREGON STATE, STENGLEN STEPHAN G, THOMAS GARY, THOMAS LAUREL, ANDERSON, ERIC, D., HAYFLICK, JOEL, S., NELSON, JAY, STATE OF OREGON, ACTING BY AND THROUGH THE OREGON, STENGLEN, STEPHAN, G., THOMAS, GARY, THOMAS, LAUREL
Application year: 1994
Main classification: C12N15
IPC codes: A61K31, A61K38, A61K48, A61P31, C07H21, C07K5, C07K14, C12N5, C12N9, C12N15, C12R1